A solid propellant rocket motor generally employs a rocket motor case, insulation, a liner composition, and a solid propellant grain in the order listed as viewed from the outer motor case to the solid propellant grain contained therein.
The functions of the motor case and insulation are well defined in the art. With the advancement of the solid propulsion art as a result of employing higher burning rate propellants, improvements in motor case materials and insulations have been needed to continue their functions in accordance with the requirements of the advanced system.
Likewise, improved liner materials have been required to be developed to meet additional conditions for the advanced propulsion systems. Additional functional requirements have also been added to the liner material, particularly, in its function as a liner-barrier material. It is a liner-barrier material for use with a propellant grain containing a high content of carboranyl burning rate accelerator to which the present invention relates.
The function of the liner is: (a) to provide the bond between the propellant and insulation with adequate adhesive strength to ensure that the interfacial bond will be capable of withstanding all of the stresses to which the propulsion subsystem may be subjected during ignition, launch, maneuver, etc., and (b) to function as a barrier to the migration of the liquid carboranyl burning rate accelerator and the other mobile constituents into the insulation, and, thus, deplete the amount of accelerator in the propellant on storage, and, consequently, adversely affect the burning rate.
To meet the combined functional needs set forth hereinabove for a liner-barrier material, it is necessary to provide a composite material wherein the primary constituent in the liner-barrier has compatibility with many resins. It is also necessary that the primary constituent be capable of being modified to further enhance the composite liner-barrier mechanical and impermeability properties.
Therefore, an object of this invention is to provide an impermeable liner-barrier for use with solid rocket propellants containing a high content of carbonaryl burning rate accelerator.
Another object of this invention is to provide an impermeable liner-barrier that is comprised of primary butyral resins which have been prepared with predetermined proportions of acetal, hydroxyl and acetate groups.
Still a further object of this invention is to provide an impermeable liner-barrier employing embedment granules and for use with a double-base propellant (such as GBZ propellant) having tensile strengths in the range of 350-400+ psi, as compared to the conventional double-base and composite propellants whose tensile strength fall in the range of 200-250 psi, and wherein the impermeable liner-barrier has increased impact resistance, peel strength, shear strength, etc. so that the bond at the interface of propellant and liner remains intact because of the enhanced adhesive properties of the liner-barrier.